Stacking armchair



FIG. 1 is a frontal perspective view of the stacking armchair showing my new design;

FIG. 2 is a right elevational view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a rear elevational view thereof.

The broken lines in the drawings illustrate the portions of the design that form no part of the claim. 

CLAIM What is claimed is the ornamental design of a stacking armchair, as shown and described. 